Vehicle with manually operated steering system

ABSTRACT

A vehicle has a manually operated steering system controlled by a steering handle, there being mounted on the steering handle an operating element which, in the event of a sudden disability of the driver, effects operation of a shutting-down system on the vehicle. The operating element comprises an electrical conductor mounted on the steering handle and functioning as a capacitive transmitter which constitutes the active capacitance in a capacitive bridge circuit for detecting a change in the effective capacitance of the capacitive transmitter, according to whether or not a driver&#39;&#39;s hand is on the steering handle. The bridge circuit operates a relay which switches off the vehicle circuits and also controls an hydraulic ram assembly which acts on a brake when the relay is operated.

United States Patent Kulick et al.

[54] VEHICLE WITH MANUALLY OPERATED STEERING SYSTEM [72] Inventors:Bruno Kulick, Bobenheim/Roxheim;

Karlheinz Lamneck, Beindersheim,

both of Germany [73] Assignee: Lansing Bagnall Limited, Basingstoke,England [22] Filed: Oct. 7, 1970 21 Appl; No.: 78,649

52 US. Cl. ..180/99, 200/52, zoo/61.57, 340/279 51 1111. C1. ..G08b21/00 [58] Field 61 Search ..200/52, 61.57; 340/279; 180/99 [56] 7References Cited UNITED STATES PATENTS 3,559,206 1/1971 Beecham ..180/99x 3,194,975 7/1965 Diamond ..200/52 3,026,503 4 3/1962 Scheer ..180/99 x2,385,982 0/1945 Gary ..180/99 2,128,916 9/1938 Cox ..340/279 3,177,4814/1965 16 et a1 ..180/99 x [4 1 Nov. 21, 1972 Myers ..200/52 PrimaryExaminer-Robert J. Spar Attorney-Martin Kirkpatrick [5 7] ABSTRACT Avehicle has a manually operated steering system controlled by a steeringhandle, there being mounted on the steering handle an operating elementwhich, in the event of a sudden disability of the driver, effectsoperation of a shutting-down system on the vehicle. The operatingelement comprises an electrical conductor mounted on the steering handleand functioning as a capacitive transmitter which constitutes the activecapacitance in a capacitive bridge circuit for detecting a change in theeffective capacitance of the capacitive transmitter, according towhether or not a driver's hand is on the steering handle. The bridgecircuit operates a relay which switches off the vehicle circuits andalso controls an hydraulic ram assembly which acts on a brake when therelay is operated.

7 Claims, 3 Drawing Figures 1 VEHICLE WITH MANUALLY OPERATED STEERINGSYSTEM The invention relates to a vehicle with a manually operatedsteering system, for example a motor vehicle, materials handling vehicleor the like.

It is desirable'to provide for vehicles of this kind precautions in theevent of any sudden disability, loss of consciousness or death of thevehicle driver, in such a way that the vehicle is immediately stopped.Such eventualities must be taken in account in view of the wide range ofstresses to which the human organism is subjected owing to therequirements of modern traffic and of the entire circumstances of life,and it is essential to prevent any major material damage or personalinjury resulting from a vehicle which has suddenly become driverless.

The prior art already discloses a so-called dead man s push-button forelectric railways, where such a pushbutton has to be depressed by thedriver from time to time and which brings the train to a stop if thebutton is not operated after a predetermined delay period. Such delayperiods, which may be of the order of magnitude of minutes in railwaytraffic, are unsuitable in traffic with steerable vehicles. In this caseit is essential to ensure that the shutting-down system comes intoeffect very rapidly but without imposing any inconvenience on thevehicle driver due to the need for normally maintaining suchshutting-down systems inoperative, that is to say without requiring anyactivities which are not related to the normal driving of the vehicle.

According to the invention, a vehicle has a manually operated steeringsystem controlled by a steering handle and an operating element which,in the event of a sudden disability of the driver, effects operation ofa shutting-down system on the vehicle, said operating element of theshutting-down system being disposed on said steering handle.

The operating element may comprise at least one electrical conductormounted on the steering handle and functioning as a capacitativetransmitter, the effective capacitance of which varies according towhether or not a drivers hand is on the steering handle. The electricalconductor may be embedded in the steering handle. In the case where thesteering handle comprises a steering wheel, the conductor may be formedby a metallic core extending around and within the steering wheel.

There may be provided a second electrical conductor, at least a part ofwhich is exposed on the surface of the steering handle, which conductoris disposed as mating electrode to the first electrical conductor so asto form part of said capacitative transmitter. In the case where thesteering handle is in the form of a steering wheel the second electricalconductor preferably extends around the steering wheel at a uniformdistance from the first said conductor.

Also in the case where a steering wheel is provided, a crank knob may bemounted upon the steering wheel, the crank knob having a metal shaftportion connected to the second electrical conductor. In the case wherethe crank knob has a shank and a head the shank of the knob preferablyincorporates said metal shaft portion.

In any of the above arrangements the capacitative transmitter formed bythe conductor or conductors may constitute the active capacitance in acapacitative bridge circuit for detecting a change in the effectivecapacitance of the capacitative transmitter.

The bridge circuit is preferably followed by a monostable switchcircuit, preferably with an amplification effect, for supplying thecontrolled current for a safety element controlling said shutting-downsystem.

The operating element provided on the steering handle may control anhydraulic circuit of the vehicle incorporating an hydraulic ram assemblywhich acts on a brake element when the cylinder of the ram assembly isdepressurized and a moveable member of which ram assembly is inadjustable connection with a switching member in the supply circuit ofan hydraulic pump in the hydraulic circuit, said switching member beingadapted to place the pump in a condition to start when the pressure inthe hydraulic cylinder drops.

The switching member may also control a valve which releases the supplyof hydraulic fluid delivered by the hydraulic pump into an hydrauliccircuit of the vehicle only if the piston of the hydraulic ram assemblyis first moved by the hydraulic pressure generated by the pump into alimiting position to release the brake element.

A valve assembly incorporating a non-return valve may be disposed upstream of the hydraulic ram assembly to release return flow from thecylinder of the ram assembly in the event of the shutting-down systembecoming operative.

The valve assembly may be constructed as a solenoid valve assembly thewinding of which is connected in an electric circuit which may beinterrupted by a relay controlled by the operating element on thesteering handle. A restrictor valve may be disposed in the supply lineto the hydraulic ram assembly.

The following is a more detailed description of one embodiment of theinvention-reference being made to the accompanying drawings in which:

FIG. 1 shows a steering wheel with a capacitative transmitter such as Ymay be used, for example, in a materials handling vehicle constructedaccording to the invention,

FIG. 2 shows a cross-section through the ring of the steering wheelshown in FIG. I and also shows the electric circuits of theshutting-down system connected to the capacitative transmitter, and

FIG. 3 shows an hydraulic circuit of the shuttingdown system controlledby the electric circuit.

The steering wheel illustrated in FIG. I is constructed in the usualmanner and comprises a ring 2 supported by three spokes 3 on a boss 5mounted on a longitudinal steering column 4.

The spokes as well as the ring of the steering wheel are provided intheir interior with a conventional metallic core 6. An electricconductor 7 is embedded in the external surface of the ring 2 around itsperiphery and is parallel to the core 6. Part of the surface of theconductor 7 is exposed so that it can come into contact with the hand ofthe vehicle driver. The two electrodes represented by the core 6 and theconductor 7 constitute the capacitative transmitter.

As can be seen at the right-hand side of FIG. I, the ring 2 of thesteering wheel is provided with a crank knob 8 of the kindconventionally employed in materials handling vehicles but also commonlyused in vehicles for the disabled. Embedded in the metal shank portionof this knob is a metal shaft 9 which in turn is mounted on a metalsleeve 10 which encircles the ring 2 and is in contact with theconductor 7. The electric circuit of the shutting-down system, to theextent to which it is connected to the moving part of the steering wheel1 or to the steering column 4, is mounted in a housing 11 disposedbetween two spokes 3 of the steering wheel. The circuit is preferablyencapsulated in the housing 11 in order to render it insensitive tovibrations.

The essential details of the electric circuit are illustrated in FIG. 2.The capacitance formed by the core 6 and the conductor 7 is connected ina capacitative bridge circuit which is fed by an oscillator 12. Thereference capacitance 13 of the bridge circuit is adapted to be variablefor matching the circuit and may be constructed in appropriate casesfrom a plurality of capacitors connected in parallel. Two halves of awinding of a transformer 14 are also connected in the bridge circuit.The output of the transformer 14 is connected to a monostable switchcircuit 15, preferably with ampliflcation characteristics. The switchcircuit 15 is disposed within the housing 11 and its outputs are broughtout by means of coaxial cable to slip-rings 16 on the steering column 4.The oscillator 12 and the switch circuit 15 are also supplied withcurrent via sliprings.

In order to reduce the risk of defective electrical contact due tovibrations, each slip-ring is preferably provided with three brusheswhich may be disposed at equal distances from one another around thering. Only one of each set of brushes is shown diagrammatically in FIG.2. Conductors extend from the brushes connected to the outputs of theswitch circuit 15 to a relay 17 which operates a contact 17a in the mainelectric circuit of the vehicle.

In this circuit the numeral 18 refers to a fuse, the numeral l9 refersto the conventional key-switch, and the numeral 20 refers to achangeover switch the function of which is explained below. Theterminals 21 and 22 are connected to the negative and positive terminalsrespectively of the vehicle battery. The terminal 23 cooperates withatraction circuit if an electric drive is provided and where appropriatecooperates with a circuit for controlling the hydraulic system of thevehicle.

The numeral 24 refers to a contactor in the supply circuit of thehydraulic pump 27 (FIG. 3) while the numerals 25 and 26 refer tosolenoid valves whose function will be described below with reference toFIG. 3.

Referring to FIG. 3, the pump 27, when operated, draws hydraulic fluidfrom the tank 35. The solenoid valve 25 is adapted, when energized, toconnect the pump 27 to the main hydraulic circuit (not shown) of thevehicle and, when deenergized to cut off the supply 'of hydraulic fluidfrom this main hydraulic circuit. The

main hydraulic circuit of the vehicle may, in the case of a fork lifttruck, control the conventional lift and tilt circuits.

When the solenoid valve 26 is energized, as shown in FIG. 3, thehydraulic fluid delivered by the pump 27 passes via a conduit 33,non-retum valve 26a, and a regulating valve 37, to the underside of thepiston 28 in an hydraulic ram assembly 29. When the solenoid valve 26 isde-energized the underside of the piston 28 is placed into communicationwith the tank 35 via a conduit 34. A spring 30, disposed within thecylinder of the ram assembly above the piston 28, urges the pistondownwardly when the ram assembly is placed into communication with thetank 35, and depresses a brake pedal 31 or some other brake element ofthe vehicle. A cam 32, having approximately the'shape illustrated inFIG. 3, is mounted on the piston rod and is adapted to act on the switch20 so that said switch starts the pump 27 via the contactor 24 when thepiston descends.

When the vehicle is at rest and the driver is not holding the steeringwheel, the electric circuit is in the condition shown in FIG. 2 and thehydraulic circuit is in the condition shown in FIG. 3, except that thesolenoid valve 25 is in a de-energized condition and will thus shut-offthe hydraulic circuit of the vehicle from the pump 27.

When the vehicle driver grips the ring 2 of the steering-wheel, a signalis transmitted form the capacitative transmitter to the switch circuit15 which causes the contact 17a to be closed. If the driver thenoperates the key switch 19, the circuit will be completed through theswitch 20 and contactor 24 and the the pump 27 is therefore energized.The pump 27 delivers hydraulic fluid through the conduit 33, non-returnvalve 26a, and regulator valve 37 to the underside of the piston 28 inthe ram assembly 29. This raises the piston 28,'against the action ofthe spring 30, and releases the brake 31. At the same time the raisingof. the cam 32 changes over the switch 20. This stops the pump 27(bymeans of the contactor 24) and energizes the solenoid valve 25. Whenthe pump 27 stops, the non-return valve 26a maintains the pressure belowthe piston 28. The energization of the solenoid valve 25 moves it to theposition shown in FIG. 3 in which the pump 27 is in communication withthe hydraulic circuit of the vehicle. The pump 27 may thus supplyhydraulic fluidto that circuit, when required, (in the case of a forklift truck, for example, to operate the lift or tilt mechanisms) whenoperated by its own electrical control circuit (not shown). Thiselectrical control circuit also includes the relay contact 17a so thatit is impossible to operate any part of the circuit after the contact17a has been opened.

Should the driver of the truck release his hold on the steering wheelfor any reason, for example through sudden loss of consciousness ordeath, then a signal will be transmitted from the capacitativetransmitter to the switch circuit 15 operating the relay 17 so as toopen the contact 17a. The relay 17 has an adjustable time delay circuitso that there is a delay between the signal being transmitted and therelay 17 operating. This ensures that the shutting-down system is nottriggered when the driver only momentarily removes his hands from thesteering knob, for example when cornering.

Opening of the contact 17a de-energizes the solenoid valves 25 and 26.De-energization of the solenoid valve 25 cuts off f the supply ofhydraulic fluid from the pump 27 the hydraulic circuit of the vehicle.If the pump 27 happens to be operating at this time it is stopped by thecontact 17a interrupting its electrical control circuit as mentionedabove. A pressure relief valve (not shown) is provided in thepumpcircuit to vent to the tank 35 any rise in fluid pressure in the circuitafter the valves 25 and 26 are operated.

De-energization of the solenoid valve 26 places the underside of thepiston 28 in the ram assembly 29 into communication with the tank 35 andthe piston 28 is therefore urged downwardly by the spring 30,

. depressing the brake pedal 31 and bringing the vehicle to a halt. Thedownward movement of the piston also changes over the switch '20 so thatthe pump 27 is ready to be started to raise the piston 28 as soon as thedrivers hand is replaced on the steering wheel, as

described above.

Should the cylinder 29 lose oil (due to a leak in the system) while thetruck is being driven normally, the piston 28 will fall and the cam 32will operate the switch 20. After this two things occur: thecontrolvalve 25 closes the lift and tilt system hydraulic circuits ofthe truck, and the pump 27 starts to run lifting piston 28 thusreleasing the brake 31. This prevents driving with partly operatedbrakes.

In the case of broken or leaking hydraulic circuits or an interruptionin the electrical circuit, which could be caused through a faultyconnection pipe, fuse, contact or one of the two solenoid valve coils,the braking system is automatically operated because the contactor 24 inthe supply circuit of the pump 27 drops out causing the de-energizedsolenoid valve 26 to allow the hydraulic fluid previously trapped underthe piston 28 to return to the tank 35. This in turn allows the pistonwhich is operated by the spring 30 to actuate the braking system. Thismeans that if a defect occurs the system automatically fails to safe.

Instead of being a capacitative transmitter, the transmitter on thesteering handle may be constructed in the form of a pneumatic orhydraulic transmitter. For example the transmitter may comprise a hosedisposed around the steering wheel and the flow cross-section of thehose may be variable under the hand pressure of the vehicle driver.

Alternatively the transmitter provided on the steering handle may be aresistive transmitter comprising two conductors which are initiallyelectrically insulated from one another but may be connected with eachother by contact with the drivers hand. The conductors then represent anon-inductive resistor which is suitably connected in a bridge circuit.

It is also possible for the transmitter to be constructed ininductive'form simply by accommodating a coil in the ring of thesteering wheel or other steering handle, said coil being connected as anactive inductance in an inductive bridge circuit. The approach of thedrivers hand to the active inductance will not substantially de-tunesuch an inductive bridge circuit, but there are cases, for example wherematerials handling vehicles are used in refrigeration houses or out ofdoors in winter, when the vehicle driver regularly wears gloves. Suchgloves may be provided in simple manner with a flexible insert of aferro-magnetic material. The hand spacing, which is unpredictable, wouldin such a case possibly exclude satisfactory adjustment of thesensitivity if a capacitative transmitter were used.

In the example shown in FIG. 1 the crank knob 8 is so constructed thatits shaft 9 terminates at a suitable distance below the top surface ofthe head of the knob so that signal transmission for triggering theshuttingdown system is not prevented by the vehicle driver, havingbecome unconscious, descending from above on to the knob. In theillustrated embodiment, the shutting-down system can be prevented fromtriggering in normal vehicle operation only by at least gripping aroundthe knob shank in the zone of the shaft 9.

We claim:

1. A vehicle having a manually operated steering system controlled by asteering handle including a steering wheel, and having, mounted on saidsteering wheel, a capacitative transmitter comprising a first electricalconductor and a second electrical conductor, said first electricalconductor being formed by a metallic core embedded within and extendingaround said steering wheel, said second conductor being spaced from saidfirst conductor and having at least a part thereof exposed on saidsteering handle, the effective capacitance of said capacitativetransmitter varying according to whether or not a drivers hand is onsaid steering handle, said capacitative transmitter constituting one armof a capacitative bridge circuit, and the vehicle also having amonostable switch circuit which follows said bridge circuitand suppliesa control current for a safety element controlling a shutting downsystem for the vehicle.

'2. A vehicle according to claim l, wherein said second electricalconductor extends around said steering wheel at a uniform distance fromsaid first electrical conductor and a crank knob is mounted upon saidsteering wheel, said crank knob having a metal shaft portion connectedto said second electrical conductor.

3. A vehicle according to claim 2, wherein said crank knob has a shankand a head, and said shank of the knob incorporates said metal shaftportion.

4. A vehicle according to claim 3, wherein said capacitative bridgecircuit controls an hydraulic circuit of the vehicle incorporatinganhydraulic ram assembly which acts on a brake element when a cylinderof said ram assembly is depressurized, a movable member of said ramassembly being in adjustable connection with a switching member in thesupply circuit of an hydraulic pump in said hydraulic circuit, saidswitching member being adapted to place said pump in a condition tostart when the pressure in said hydraulic cylinder drops.

5. A vehicle according to claim 4, wherein said switching member alsocontrols a valve which releases a supply of hydraulic fluid delivered bysaid hydraulic pump into said hydraulic circuit of the vehicle only ifthe piston of said hydraulic ram assembly is first moved by hydraulicpressure generated by said pump into a limiting position to release saidbrake element.

6. A vehicle according to claim 5, wherein a valve assemblyincorporating a non-return valve is disposed upstream of said hydraulicram assembly to release return flow from said cylinder of said ramassembly in the event of said shutting-down system becoming operative.

7. A vehicle having a manually operated steering system controlled by asteering wheel, a first electrical conductor and a second electricalconductor extending around said steering wheel, said first conductorbeing formed by a metallic core embedded in the steering wheel, saidconductors being spaced from one another to form a capacitativetransmitter the effective capacitance of which varies according towhether or not a drivers hand is on said steering wheel, saidcapacitative transmitter constituting one arm of a capacitative bridgecircuit, and the vehicle also having a monostable switch circuit whichfollows said bridge circuit and supplies a control current for a safetyelement controlling a shutting down system for the vehicle.

1. A vehicle having a manually operated steering system controlled by asteering handle including a steering wheel, and having, mounted on saidsteering wheel, a capacitative transmitter comprising a first electricalconductor and a second electrical conductor, said first electricalconductor being formed by a metallic core embedded within and extendingaround said steering wheel, said second conductor being spaced from saidfirst conductor and having at least a part thereof exposed on saidsteering handle, the effective capacitance of said capacitativetransmitter varying according to whether or not a driver''s hand is onsaid steering handle, said capacitative transmitter constituting one armof a capacitative bridge circuit, and the vehicle also having amonostable switch circuit which follows said bridge circuit and suppliesa control current for a safety element controlling a shutting downsystem for the vehicle.
 1. A vehicle having a manually operated steeringsystem controlled by a steering handle including a steering wheel, andhaving, mounted on said steering wheel, a capacitative transmittercomprising a first electrical conductor and a second electricalconductor, said first electrical conductor being formed by a metalliccore embedded within and extending around said steering wheel, saidsecond conductor being spaced from said first conductor and having atleast a part thereof exposed on said steering handle, the effectivecapacitance of said capacitative transmitter varying according towhether or not a driver''s hand is on said steering handle, saidcapacitative transmitter constituting one arm of a capacitative bridgecircuit, and the vehicle also having a monostable switch circuit whichfollows said bridge circuit and supplies a control current for a safetyelement controlling a shutting down system for the vehicle.
 2. A vehicleaccording to claim 1, wherein said second electrical conductor extendsaround said steering wheel at a uniform distance from said firstelectrical conductor and a crank knob is mounted upon said steeringwheel, said crank knob having a metal shaft portion connected to saidsecond electrical conductor.
 3. A vehicle according to claim 2, whereinsaid crank knob has a shank and a head, and said shank of the knobincorporates said metal shaft portion.
 4. A vehicle according to claim3, wherein said capacitative bridge circuit controls an hydrauliccircuit of the vehicle incorporating an hydraulic ram assembly whichacts on a brake element when a cylinder of said ram assembly isdepressurized, a movable member of said ram assembly being in adjustableconnection with a switching member in the supply circuit of an hydraulicpump in said hydraulic circuit, said switching member being adapted toplace said pump in a condition to start when the pressure in saidhydraulic cylinder drops.
 5. A vehicle according to claim 4, whereinsaid switching member also controls a valve which releases a supply ofhydraulic fluid delivered by said hydraulic pump into said hydrauliccircuit of the vehicle only if the piston of said hydraulic ram assemblyis first moved by hydraulic pressure generated by said pump into alimiting position to release said brake element.
 6. A vehicle accordingto claim 5, wherein a valve assembly incorporating a non-return valve isdisposed upstream of said hydraulic ram assembly to release return flowfrom said cylinder of said ram assembly in the event of saidshutting-down system becoming operative.